Massachusetts Rep. Barney Frank says he decided not to seek re-election to a 17th term in 2012 because congressional redistricting would have given him a slew of new constituents and a difficult, expensive campaign.

"I think I would have won," Frank, 71, said during a Monday press conference in Massachusetts announcing his retirement. "But it would have been a tough campaign."

Added Frank, who has led financial reform efforts on Capitol Hill: "I don't like raising money."

The former chairman and current ranking member of the House Financial Services Committee said he would "acknowledge one error" during his more than three decades on Capitol Hill (a vote against the 1990 U.S. invasion of Iraq.)

And he launched a vigorous defense of his role in the sub-prime mortgage lending and housing bubble fiasco.

But mostly, the first member of Congress to voluntarily disclose that he was gay and who says he always planned to leave the Hill when he turned 75, seemed relieved.

He won't have to raise millions for a tough re-election fight, he said. He won't have to traverse a newly drawn district and persuade people they should elect him for one term. And, he says, he'll be leaving a Congress diminished in the eyes of the American people and dysfunctional at a level many have not seen before.

"I am, however, not retiring from advocacy of public policy," Frank said. By all indications Monday, Frank will also continue to weigh in on presidential politics.

"I did not think I've lived a good enough life to be rewarded by Newt Gingrich being the Republican nominee," Frank said, adding that he relished the prospect of debating the thrice-married Gingrich on the merits of the Defense of Marriage Act that bars same-sex marriages.

Gingrich, the former House Speaker who is leading in national GOP presidential preference polls, would be the "best thing to happen to Democrats since Barry Goldwater," quipped Frank, who served in Congress with Gingrich in the 1990s.

Taking another shot at Gingrich, Frank said he would be "neither a lobbyist nor a historian" when he leaves Congress. Gingrich recently explained that he was paid handsomely by government-backed lender Freddie Mac to provide advice as a "historian."

When he steps down next year, Frank will leave a legacy of civil rights activism on behalf of gay Americans.

That activism, says gay rights leader Joe Solmonese, culminated recently with the repeal of a law barring openly gay Americans from serving in the U.S. military.

"No two people have been more responsible for the advancement of LGBT equality than Barney Frank and [the late Massachusetts Sen.] Ted Kennedy," says Solmonese, who heads Human Rights Campaign, the nation's largest gay rights organization.

"Barney laid the groundwork for all the successes we have had - from the repeal of the military's Don't Ask, Don't Tell, to the passage of the Matthew Shepard and James Byrd Jr. Hate Crimes Prevention act," Solmonese says.

"They never would have happened without his leadership," he said.

Republican rainmakers will also lose an enduring foil. The GOP has raised untold millions using the cantankerous Democratic lawmaker, as well as Minority Leader Nancy Pelosi, as a symbol of an "out-of-control, spending, over-regulating Congress," says Massachusetts-based GOP consultant Todd Domke.

"Republicans are losing a liberal Massachusetts Democrat who has been a great fundraising tool," Domke says.

Frank's ties with mortgage giants Fannie Mae and Freddie Mac, and his role shepherding through the Dodd-Frank financial regulation bill will continue to fuel the Republican case against Democrats, Domke says.

"Part of his legacy from Republicans' point of view is that he was complicit in the housing crisis that precipitated the collapse," he said.

While fans of Frank acknowledge his famous impatience and temper, they routinely ascribe it to his intellect.

"The problem for Barney is that his brain works faster than anyone else's," says Solomese, who once worked for the congressman. "He's incredibly impatient, but it's all grounded in his passion."

"One instance he may be biting off your head for getting directions wrong, and the next he'd be asking how my mother's doing," he said.

Domke is among those who find more arrogance than passion in Frank's demeanor.

"It wasn't just not suffering fools gladly. In his case, it was not suffering anyone," he said. "He didn't enjoy the last campaign at all."

His decision not to run, Domke says, is an indication that Frank believes Republicans will retain majority control of the House, and he would not again become chairman of the financial services committee.

That being said, Frank "was a gay rights pioneer," Domke says, "who set an example of personal courage that affected a lot of people."

Part of that example? That after coming out in the 1980s, he continued to win re-election - even after he was reprimanded by the House for fixing parking tickets for a male prostitute friend - and "showed that this didn't have to be an abiding prejudice."